package kook

import (
	"context"
	"encoding/json"
	"fmt"
	"net/url"
)

// gatewayResult is the "data" payload of GET /gateway/index.
type gatewayResult struct {
	URL string `json:"url"`
}

// fetchGatewayURL retrieves the gateway WebSocket address from the KOOK REST
// API. compress=0 requests uncompressed delivery so every server->client frame is
// plain JSON text, matching wsutil's reader.
func (a *Adapter) fetchGatewayURL(ctx context.Context) (string, error) {
	data, err := a.http.GetJSON(ctx, gatewayPath, url.Values{"compress": {"0"}})
	if err != nil {
		return "", fmt.Errorf("kook: fetch gateway: %w", err)
	}
	var res gatewayResult
	if err := json.Unmarshal(data, &res); err != nil {
		return "", fmt.Errorf("kook: decode gateway result: %w", err)
	}
	if res.URL == "" {
		return "", fmt.Errorf("kook: gateway url empty: %w", ErrBadResponse)
	}
	return res.URL, nil
}